update-major.yml

name: Update major tag

on:
  # Run when a release tag is pushed
  push:
    branches-ignore:
      - '**'
    tags:
      - 'v*.*.*'

permissions:
  contents: write

jobs:
  # When a release tag is pushed, update the matching short
  # version tag, for example v2
  update-tags:
    runs-on: ubuntu-20.04
    steps:

      # Check out this repository at the same ref that triggered
      # this workflow run
      - uses: actions/checkout@v2

      - name: Configure Git client
        run: |
          _user="${{ github.repository_owner }}"
          _email="${_user}@users.noreply.github.com"
          git config user.name "${_user}"
          git config user.email "${_email}"

      # Update short version tag, for example v2
      - name: Update major version tag
        id: roll-tag
        run: |
          # Set up variables.
          _tag="${INPUT_TAG:-${GITHUB_REF#refs/tags/}}" # v2.2.0
          _major="${_tag%%.*}"                          # v2
          _msg="Release ${_tag}"
          _curr="$(GITHUB_TOKEN=${{ github.token }} \
                  gh api /repos/:owner/:repo/releases/latest | \
                  jq -r .tag_name)"
          # If tag pushed is not for latest release, exit early
          if [ "$_tag" != "$_curr" ]; then
            echo "SKIP: Tag pushed ($_tag) is not for latest release."
            exit 0
          fi
          # Update _major tag
          git tag -fa "${_major}" -m "${_msg}"
          # Push _major tag
          git push --force origin "${_major}"